Electronic displays are normally designed to have high brightness when viewed head-on or from the sides. Some displays, like televisions, have wide viewing angles to accommodate large audiences; these displays appear bright even when viewed at a large viewing angle. Others, like laptop screens, have a narrower viewing angle: when the display is viewed head-on it is bright, but if viewed from an angle it becomes dark. This increases power efficiency. By contrast, diffuse surfaces like paper, painted walls, fabric scraps, or many natural objects have a nearly uniform brightness over all viewing angles, and no sharp change in intensity or character is noticeable when the viewing angle of such surfaces is changed.
Electronic displays are commonly mounted on diffuse surfaces. But if an electronic display is meant to mimic a natural object, like being a seamless part of a wall or replacing a photograph, it should have the same brightness at each viewing angle as the natural object. Otherwise at certain viewing angles it becomes a virtual “hole,” a dark and visually distracting rectangle on the diffuse background.